TYK2 and rheumatoid arthritis: Tofacitinib acts by blocking JAK1 and JAK3 but has also a role in JAK2 and TYK2 inhibition and is the first oral JAK-i approved for the treatment of RA[19,20,21] and psoriatic arthritis (PsA).[22] Baricitinib is a JAK1 and JAK2 inhibitor used in RA treatment,[23] such as filgotinib[24,25] and upadacitinb,[26,27] that inhibits more selectively JAK1.